At a guess you left the country set to UK when you entered the waypoints. Select 'Any' and try it.
After clicking Plan, look at the list of waypoints that it has found. If you've set the country to UK and enter 'EINN' it can't find it, so it tries to find something else that you might have meant. The best it can find is 'Alsop en le Dale' (presumably because 'en' sounds a bit like 'einn') so it uses that. BEFORE clicking on the map link you can select from the various other choices that it has offered.